Quality Evaluation of Dry Sweet Basil Leaves with Comparative Analysis of Aroma Compounds and Leaf Tissue Structure

Abstract

A quality evaluation method for dried herbs was studied with sweet basil leaves (fresh, air-dried, freeze-dried and vacuum-dried sweet basil leaves) as herbal teas, involving hot-water extraction. Sensory evaluation revealed that the flavor of herbal tea with vacuum-dried sweet basil leaves was similar to that with fresh leaves. Seven odor-active compounds (cineole, linalool, eugenol, octanal, 1-octanol, (E)-2-hexenal and (Z)-3-hexenol) from herbal teas were identified by capillary gas chromatographic-mass spectrometry and olfactometry analysis, and it was considered that three compounds (octanal, (E)-2-hexenal and (Z)-3-hexenol) were key compounds for describing the results of sensory evaluation. The structure of dried sweet basil leaves with water-absorption and fresh leaves was observed by differential interference contact microscopy, and their rheological characteristics were measured for storage modulus. As a result, the characteristics of vacuum-dried sweet basil were similar to those of fresh basil. These results suggest that investigation of the aroma using hot-water extraction, tissue structure and rheological characteristics could be effective approaches to qualitatively evaluate dried herbs.